Question: Why does our bodies need protecting so much in space

Julia Attias answered on 5 Dec 2015:

Hi 685nch28,

This is a great question – one of the fundamentals in fact. We have all been born into an environment that has gravity, which means that our body grows and adapts to the environment it is in. We barely experience more than 8 hours of each of our days (when we are sleeping) without being exposed to it… If you then suddenly go into an environment that doesn’t have gravity, all of those processes and functions of your body that are so used to being “in gravity” will change, because its not what they are used to.

So unfortunately, the majority of these functions and processes change when we take ourselves away from gravity, which can cause problems for the astronauts. I’ll give you an example: we stand on Earth all day every day and fight the force of gravity in doing so; in space there is no standing, so the muscles responsible for standing on Earth get weaker (the leg muscles). However, if astronauts were to go to space and not come back, because their body wouldn’t be exposed to gravity again, they wouldn’t have to fight the gravity away when standing, so it wouldn’t matter that those muscles are weaker. But… they come back to Earth! Which means they will need to stand again, and those muscles will need to work against gravity when they get back, so the astronauts have to keep them strong whilst they are in space so that they are still capable of standing when they get back!